Avatars are used in many applications. One of them is computer-aided design: the designer needs them to simulate the interaction of a building, object, piece of furniture, machine or the like with people—e.g. to study the ergonomics of an airplane seat. Other applications are videogames and cinematographic animation. Therefore, graphic software often provides a library of predefined avatars and tools to configure them, e.g. by changing their morphology.
Most often, avatars wear clothes and sometimes accessories such as hats or jewels. This is required to obtain a realistic representation, and sometimes also for functional reasons (e.g. the ergonomics of a seat can be very different depending on the clothes worn by a user).
Both avatars and garments are usually represented by digital models stored in a library of a computer graphics system.
There is then a need for a tool allowing adapting the digital model of a garment to the morphology and size of an avatar. For example, the model of a dress has to be adapted to wearers of different sizes and morphologies. Ideally, if the morphology or size of the avatar is changed, the garment should adapt itself quickly and with minimal or no need for user intervention. In particular, such a software tool should be able to identify and solve “collisions” or “clash”, i.e. situations where some parts of a garment are situated inside the body of the avatar.
Several approaches are known from the prior art to fulfill this need.
The paper by R. Brouet et al, “Design Preserving Garment Transfer”, ACM Transaction of Graphics (TOG) Proceedings of ACM SIGGRAPH 2012 Volume 31 Issue 4, July 2012, describes a method which allows transferring a garment designed to be adapted to a “reference” body to a different “target” body. The main drawback of this method is that the reference body needs to be known: the method does not allow extracting a garment from a library and adapting it to an avatar. Moreover, it is complex, and therefore slow (several minutes of processor time may be required for adapting reasonably complex garments.
The DRAPE system, described in the paper by Peng Guan et al. “DRAPE: DRessing Any PErson”; ACM Trans. on Graphics (Proc. SIGGRAPH), 31(4):35:1-35:10, July 2012; is a complete system for animating clothes on synthetic bodies with different shapes and poses. It makes use of a model of clothing which is learned from a database of physics-based simulations. Applying this method to the problem considered here, where a garment has to be adapted to an indefinite number of different avatars, would be too complex. Moreover, it has been found that DRAPE can lead, in some cases, to unrealistic results. A subset of DRAPE, used for refining the fit of a garment, does not need such a database of physics-based simulation and can directly be applied to any mesh representing a garment. However it is only adapted to minor modifications of the avatar and it could not be used, for instance, to adapt a dress to a pregnant woman.